Network-initiated data transfer in a mobile network

ABSTRACT

A method for IP [=Internet Protocol] communication to/from a mobile terminal via a network element in a mobile network. The mobile terminal uses an in-band trigger for establishing an IP connection. The network element uses an out-band trigger ( 3 - 8 ) for initiating IP connection establishment. The mobile terminal responding to the out-band trigger by using an in-band trigger for establishing the IP connection ( 3 - 10 ). After the data transfer ( 3 - 12 ), the mobile terminal and the network element maintain the IP connection for a predetermined time after the latest transaction ( 3 - 14 ).

A. BACKGROUND OF THE INVENTION

The invention relates to techniques which are colloquially referred toas pushing data. Expressed more formally, the invention relates tomethods, equipment and program products for network-initiated datatransfer in a packet-switched mobile network.

In a packet-switched mobile network, a mobile terminal does is notnormally assigned a dedicated circuit-switched connection. Instead, thenetwork establishes and maintains a session for the terminal, and datapackets are sent when necessary. In order to integrate mobile terminalswith office applications, it is becoming increasingly popular tomaintain Internet Protocol (IP) connections over packet data channels inpacket-switched mobile networks. Maintaining an IP connection to/from amobile terminal is desirable in order to keep data banks synchronizedbetween the mobile terminal and an office computer, for example.

Maintaining an IP connection in packet-switched mobile networks involvescertain problems, however. For example, it consumes the mobileterminal's battery. Further, many networks apply operator-definedpolicies to break connections after a certain period of inactivity. Whenthe IP connection to/from the mobile terminal is disconnected, databasesynchronization is impossible before connection re-establishment.Connection re-establishment must be initiated from the mobile terminal'sside, the network cannot initiate connection re-establishment.

But connection re-establishment involves further expenses in tariffand/or battery consumption. Yet further, since the network cannotinitiate re-establishment of the IP connection, network-initiated datasynchronization must be initiated by means of an out-band trigger, i.e.,signalling independent from the Internet Protocol. A short messageservice (SMS) and its derivatives are examples of theoretically suitableout-band triggering mechanisms. But a single GSM-compliant short messagecan only transfer approximately 160 characters, which means that it isimpracticable to transfer actual data in the trigger message. This hasthe consequence that the subscriber must bear the expenses and delays inre-establishing the IP connection.

B. BRIEF DESCRIPTION OF THE INVENTION

An object of the present invention is to provide a method and anapparatus for implementing the method so as to alleviate the abovedisadvantages. The object of the invention is achieved by the methodsand equipment which are characterized by what is stated in theindependent claims. The dependent claims relate to specific embodimentsof the invention.

The invention is based on the idea that a mobile terminal uses anin-band trigger for establishing an IP connection. The network element,when it needs to communicate with the mobile terminal, uses an existingIP connection if one is available; and if not, uses an out-band triggerfor initiating the IP connection establishment. The mobile terminalresponds to the out-band trigger by using an in-band trigger forestablishing the IP connection. The IP connection is maintained for apredetermined time after the latest transaction (in either direction).

If no out-band trigger for initiating IP connection establishment isavailable, the mobile terminal enters a periodic polling mode, whereinit periodically sends inquires to or via the network element for dataitems to be synchronized.

An aspect of the invention is a method according to claim 1. Anotheraspect of the invention is a method according to claim 2. Other aspectsof the invention relate to computer systems or program products forimplementing the above methods.

C. BRIEF DESCRIPTION OF THE DRAWINGS

In the following the invention will be described in greater detail bymeans of specific embodiments with reference to the attached drawings,in which:

FIG. 1 shows an exemplary network arrangement in which the invention canbe used;

FIG. 2 shows a flowchart illustrating the principle of the invention asseen from the point of view of the network element; and

FIG. 3 shows a flowchart illustrating the principle of the invention asseen from the point of view of the mobile terminal.

D. DETAILED DESCRIPTION OF SPECIFIC EMBODIMENTS

The invention is applicable to virtually any mobile networkarchitecture. The mobile network may be based on GPRS, 1xRTT or EVDOtechnologies, for example. The invention can also be implemented as partof a push-type mobile e-mail system, particularly in a consumer e-mailsystem, in which optimization of network resources is important becauseof the large number of users.

FIG. 1 shows an exemplary system architecture which is supported by theowner of the present application. This system supports synchronizationof e-mail messages and/or calendar items and/or other informationbetween a host system and a mobile terminal.

Reference numeral 100 denotes a host system that is able to send anreceive e-mail messages. Reference numeral 102 denotes a mobileterminal, also able to send an receive e-mail messages. The e-mailmessages may originate or terminate at external e-mail terminals, one ofwhich is denoted by reference numeral 104. The invention aims atimproving cooperation between the host system 100 and mobile terminal102 such that they can use a single e-mail account as transparently aspossible. This means, for example, that the users of the external e-mailterminals 104, when sending or receiving e-mail, do not need to know ifthe user of the host system 100 actually uses the host system 100 or themobile terminal 102 to communicate via e-mail. The transparency alsomeans that e-mail manipulation at the mobile terminal 102 has, as far aspossible, the same effect as the corresponding e-mail manipulation atthe host system 100. For example, e-mail messages read at the mobileterminal 102 should preferably be marked as read at the host system.

Reference numeral 106 denotes a data network, such as an IP (InternetProtocol) network, which may be the common Internet or its closedsubnetworks, commonly called intranets or extranets. Reference numeral108 denotes an e-mail server and its associated database. There may beseparate e-mail servers and/or server addresses for incoming andoutgoing e-mail. The database stores an e-mail account, addressable bymeans of an e-mail address, that appears as a mailbox to the owner ofthe e-mail account. In order to communicate with mobile terminals 102,the data network 106 is connected, via a gateway 112 to an accessnetwork 114. The access network comprises a set of base stations 116 toprovide wireless coverage over a wireless interface 118 to the mobileterminals 102.

Reference numeral 110 denotes a messaging centre that is largelyresponsible for providing the above-mentioned transparency between thehost system 100 and the mobile terminal 102. The system architecturealso comprises a connectivity function 120, whose task is to push e-mailmessages to the mobile terminal. In the embodiment shown in FIG. 1, theconnectivity function 120 is considered a physically integral butlogically distinct element of the messaging centre 110.

The mobile terminal 102 may be a pocket or laptop computer with a radiointerface, a smart cellular telephone, or the like. Depending onimplementation, the host system 100, if present, may have differentroles. In some implementations the host system 100 is optional and maybe a conventional office computer that merely acts as the mobileterminal user's principal computer and e-mail terminal. In otherimplementations the host system may act as a platform for a singleuser's connectivity function, in addition to being an office computer.In yet other implementations the host system 100 may comprise theconnectivity function for several users. Thus it is a server instead ofa normal office computer.

We assume here that the access network 114 is able to establish andmaintain a IP connection 122 between the messaging centre 110 and themobile terminal 102.

FIG. 1 shows an embodiment in which the messaging centre 110 is largelyresponsible for e-mail transport to/from the mobile terminal 102 via theaccess network 114, while a separate connectivity function 120 isresponsible for data security issues. The connectivity function 120 maybe physically attached to or co-located with the messaging centre 110,but they are logically separate elements. Indeed, a definite advantageof the separate connectivity function 120 is that it can be detachedfrom the messaging centre, for instance, within the company that ownsthe host system 100 or the e-mail server 108. For a small number ofusers, the connectivity function 120 can be installed in each hostsystem 100, or the host system 100 can be interpreted as a separateserver configured to support multiple users. It is even possible toimplement some or all the above-mentioned options. This means, forexample, that there is one or more messaging centres 110 that offerservices to several network operators, or they may be a dedicatedmessaging centre for each network operator (somewhat analogous to shortmessaging centres). Each messaging centre 110 may have an integralconnectivity function 120 to support users who don't wish to install aseparate connectivity function in a host system 100. For users who doinstall a separate connectivity function 120 in their host systems 100,such connectivity functions bypass the connectivity function in themessaging centre 110 and address the messaging centre 110 directly.

A real e-mail system supports a large number of mobile terminals 102 andIP connections 122. In order to keep track of which e-mail account andwhich IP connection belongs to which mobile terminal, the messagingcentre 110 and the connectivity function collectively maintain anassociation 124, 124′ for each supported mobile terminal. Basically,each association 124, 124′ joins three fields, namely an e-mail address124A assigned to the mobile terminal or its user, encryption information124C and a temporary wireless identity 124D of the mobile terminal inthe access network. The embodiment shown in FIG. 1 also employs aterminal identifier 124B which may be the same as the e-mail address124A of the mobile terminal 102, in which case the association 124actually associates three information items. Alternatively, the terminalidentifier 124B may be an identifier arbitrarily assigned to the mobileterminal. In a preferred implementation the terminal identifier 124B isthe mobile terminal's equipment identifier or its derivative. Theencryption information 124C is preferably related to the mobileterminal's equipment identity and is preferably generated by the mobileterminal itself, so as to ensure that no other terminal besides the oneused for creating the encryption information 124C will be able todecrypt incoming encrypted e-mail messages. The temporary wirelessidentity 124D may be the identifier of the IP connection 122 to themobile station.

In the above-described system, the messaging centre 110 and connectivityfunction 120 were arranged to support a fairly large number of users ofe-mail and/or calendar data. In order to satisfy the needs of thepresent invention, virtually any communication server able to maintainan IP connection to the mobile terminal can be used.

In order to provide out-band triggers, the network arrangement isoperationally coupled to a network element able to communicate to themobile terminal even in the absence of an IP connection. In the networkarrangement shown in Figure, such a network element is embodied as ashort message service centre (SMSC) 126. Because the IP connectioncannot be initiated from the network side, the messaging centre 110 (orany other communication server) must request the mobile terminal 102 toestablish the IP connection, for example when data needs to besynchronized between the mobile terminal and some other node, such asthe host system 100. Such a request to establish the IP connection canbe sent in the form of a connectionless message, such as a short messageor one of its derivatives, for example, a multimedia message.

FIG. 2 shows a flowchart illustrating the principle of the invention asseen from the point of view of a network element, such as the messagingcentre 110 shown in FIG. 1, or some other element or servercommunicating with the mobile terminal. Step 2-2 is a loop in which thenetwork element waits for a need to transfer data to the mobileterminal. In step 2-4 the network element determines if an IP connectionto the mobile terminal is available. If yes, the IP connection will beused in step 2-6. After step 2-6 the process continues to step 2-16 inwhich the IP connection will be kept active for a predetermined timeafter, in order to avoid the expenses incurred in re-establishing adiscontinued IP connection.

If no IP connection to the mobile terminal was not available in step2-4, the process continues to step 2-8, in which the network elementdetermines if an out-band triggering means, such as a short messageservice, is available. If not, the process continues to step 2-10, inwhich the network element resorts to mobile-initiated polling. In otherwords, the network element has no means to initiate IP connectionestablishment to the mobile terminal and must wait for inquiries fromthe mobile terminal. On the other hand, if an out-band triggering means,such as a short message service, is available, it will be used in step2-12. In response to the trigger, the mobile terminal establishes an IPconnection which the network element will use in 2-14, after which theprocess continues to step 2-16.

FIG. 3 shows a flowchart illustrating the principle of the invention asseen from the point of view of the mobile terminal. In step 3-2 themobile terminal determines if an out-band triggering means is available.If not, the mobile terminal knows that the network element cannotrequest IP connection establishment, and in step 3-4 the mobile terminalenters a periodic polling mode, in which it periodically polls thenetwork element for new information.

The mobile terminal makes the test in step 3-2 not for its own benefitbut for the network element's, because the mobile terminal can alwaysinitiate IP connection establishment. But if no out-band triggeringmeans is available, the mobile terminal knows that it cannot expect arequest from the network element to establish an IP connection, which iswhy it should periodically poll the network element for new data.

When the system is in the periodic polling mode, at certain periodicintervals, the mobile terminal establishes an IP connection forinquiring the network element for new data, even if the mobile terminalitself has no data to send. If the network element has data to send, theIP connection is preferably kept active for a predetermined time afterthe latest data transfer. This procedure will be further described inconnection with step 3-14.

In step 3-6, if the mobile terminal detects a need to transfer data, itproceeds to step 3-10 to establish an IP connection with the networkelement. Likewise, the IP connection establishment is initiated if instep 3-8 an out-band trigger is received from the network element. Afterthe IP connection establishment in step 3-10, the mobile terminaltransfers data in step 3-12, and in step 3-14 it keeps the IP connectionactive for a predetermined time after the latest transaction (in eitherdirection).

In steps and 2-16 and 3-14, the IP connection is kept active for apredetermined time after the latest transaction (in either direction),in order to avoid the expenses in re-establishing a disconnected IPconnection. This step can be implemented, for example, by means of twotimers (physical or logical). Let us assume, for example, that thenetwork disconnects IP connections after an inactivity period of 5minutes. Let us further assume that, for the sake of economy andconvenience, the IP connection will be maintained for 15 minutes afterthe latest transaction. After each transaction, both timers will bestarted. When the 5-minute timer expires, a keep-alive message is sentto the other party. A keep-alive message is a message sent for thepurpose of preventing the network from disconnecting the IP connection.When the keep-alive message is sent, the 5-minute timer is againrestarted, until the 15-minute timer expires, after which the keep-alivemessages will no longer be sent.

It is readily apparent to a person skilled in the art that, as thetechnology advances, the inventive concept can be implemented in variousways. The invention and its embodiments are not limited to the examplesdescribed above but may vary within the scope of the claims.

1. A method for Internet Protocol communication from a communicationsserver to a mobile terminal, the method comprising: receiving data forcommunication to the mobile terminal, the data received at thecommunications server; identifying the unavailability of an InternetProtocol connection with the mobile terminal; initiating the delivery ofan outbound trigger for establishing an Internet Protocol connectionwith the mobile network to the mobile terminal in response to thedetermination that an Internet Protocol connection is unavailable;establishing an Internet Protocol connection with the mobile terminalvia the mobile network, the Internet Protocol connection established inresponse to the mobile terminal having responded to the outbound triggerthrough use of an inbound trigger; transferring the data forcommunication to the mobile terminal to the mobile terminal; commencinga first timer at the communications server following transfer of thedata to the mobile terminal; sending a keep-alive message over theInternet Protocol connection following expiration of the first timer atthe communications server; recommencing the first timer at thecommunications server following the sending of the keep-alive message;commencing a second timer operating independent of the first timer atthe communications server; terminating sending of keep-alive messagesupon expiration of the second timer; and disconnecting from the InternetProtocol connection following expiration of the first timer.
 2. Themethod of claim 1, wherein the outbound trigger is sent from a shortmessaging service center in response to instructions from thecommunications server.
 3. The method of claim 2, wherein the outboundtrigger is a short message service message.
 4. The method of claim 1,wherein the first and second timers are physical.
 5. The method of claim1, wherein the first and second timers are logical.